Retracting boom crane



April 15, 1947. H. G. HILLS 2,419,138

BETRACTING BOOM CRANE Filed Sept. 19, 1945 L i 4 i c 56 L 58 JNVENTOR. HHROLD 6. HILLS HTToR/vtrJ shown in Fig. 1; 1

Fig. 3 is a sectional view approximately on the.

Patented Apr. 15, 1947 UNITED STATES PATENT OFFICE W ellman Engineering Company,

Cleveland,

Ohio, a corporation of Ohio Application September 10, 1945, Serial No. 615,335

1 Claim.

The present invention relates to retracting boom cranes and, particularly, to control mechanisms for preventing the trolley assembly thereof from running oil? the end of the boom or from hitting the end stops in the event the boom is provided with end stops.

One of the principal objects of the invention is the provision of a novel automatic control mechanism for limiting the travel of a trolley relative to the ends of a retracting boom crane regardless of the position of the boom.

Another object of the invention is the provision of a novel power actuated drive for the trolley assembly of a retracting boom crane, in combination with means for stopping the drive as the trolley assembly approaches one or both ends of the boom. 4

Another object of the invention is the provision of a novel retracting boom crane comprising means for reciprocating the boom, power actuated means for reciprocating the trolley assembly along the boom, and means for automatically stopping the drive means for the trolley assembly as the trolley assembly approaches adjacent to the end of the boom regardless of the position of the boom.

Another object of the invention is the provision of a novel retractin .boom crane comprising power actuated drive means for reciprocating the boom, power actuated drive means for reciprocating the trolley assembly along the boom, and

means for automatically stopping either or both relates from the following disclosure and description of the preferred embodiment made with ref erence to the accompanying drawings forming a part of this specification in which similar reference characters designate corresponding parts, and in which:

Fig. 1 is a plan view of a retracting boom crane embodying the present invention;

Fig. 2 is a side elevational view of the crane line 3-3 of Fig. 2; and

Fig. 4 is an enlarged detail view of part of the control mechanism shown in Fig. 1.

'Generally speaking, the invention contemplates the provision of a retracting boom crane having a movable boom assembly and a movable trolley assembly supported thereon, in combination with power actuated means for moving the trolley, and means operatively connected to the boom, the trolley and the control means associated with the power actuated means which moves the trolley for stopping the trolley prior to its reaching the end of the boom regardless of the position of the boom; in other words, the power actuated means for moving the trolley cannot be operated to run the trolley off the end of the boom or into the end stops if such are provided. If the boom is reciprocated by power actuatedmeans, as is the preferred embodiment hereinafter referred to,-the invention also contemplates means for stopping the power actuated mechanism for reciprocating the boom immediately'prior to either or bothends of the boom reaching the trolley.

Referring to the drawings, the reference character A designates generally an overhead trolley supported for movement along a reciprocable or retlactible boom B. The type of trolley employed forms no part of the present invention and is not shown 01' described in detail. Suffice it to say that the trolley A comprises a frame member It provided with a plurality of wheels I! through the medium of which it is movably supported upon the lower flange of the boom B which, as shown, is in the form of an I-beam. Any suitable load supporting grab may be attached to the trolley.

, Ihe boom B is movably supported by a plurality of rollers l2 connected to brackets H, which brackets are, in turn, connected to suitable supports, such as, the columns !4 shown. The rollers i2 engage underneath the upper flange of the boom B. End stops [5 at opposite ends of the boom B prevent the trolley A from accidentally running on" the end of the boom. Alternatively any suitable type of retracting or movable boom may be employed in place of the particular construction shown.

The trolley is adapted to be reciprocated along the boom B by a cable iiilooped about a pulley l'l keyed to a shaft is rotatably supported in suitable bearing members or journal boxes 20,2! on a platform 22 connected to two of the columns l4. .Fromthe pulley i! opposite reaches of the cable l6 extend around guide pulleys 23 connected to opposite ends of the boom B. After passing around the lower guide pulleys 23 the ends ofthe cable are connected to the trolley. The construction is such that the trolley A is reciprocated along the boom B upon rotationof ,the shaft l8 and, in turn, the pulley I! in opposite directions. Accordin to the provisions of the present invention, the shaft I8 is adapted to be rotated in opposite direction by power means. In the embodiment shown this power means is a reversible electric motor 25 supported on the platform 22 and connected to the shaft It by suitable reduction gears, designated generally as 26,

The boom 13 is adapted to be reciprocated by a reversible electric motor 21 on the platform 22. The motor 27 is connected to a shaft 23 by suitable reduction gears 39. The shaft 28 is rotatably supported in suitable bearings 3!, 32 connected to the platform 22 and is provided at its forward end with a gear 33 continuously in mesh with a rack es fixed to the upper flange of the boom B. Alternatively the motor 21 and the gearing 39 may be omitted and the boom B reciprocated by hand. As a matter of convenience, the left-hand end of the boom, as viewed in Figs. 1 and 2, will be referred to as the front end and the right-hand end referred to as the rear end.

Th electric motors 25, 21 are of commercial construction and are operated by conventional control mechanism, modified in a manner hereinafter specifically pointed out, from a control station connected to one of the columns M or located at some other convenient place. According to the provisions of the present invention, the control mechanism for the motors 25, 2'! includes differentially-operated limit switch means for preventing either motor from being operated to cause engagement between the trolley A and the end stops of the boom B; in other words, the control mechanism is so arranged as to permit only sufiicient individual operation of the motors 25, 27 to cause the trolley A to travel a distance slightly less than the length of the boom 13.

A shown, the shafts i3, 28 which are operatively connected to the motors 25, 21, respectively, are connected by means of difierential gearing mechanism C to a limit switch assembly D having two sets of normally closed limit switches Q0, 4!, i2, 33 and 4 d5, 16, il controlled by a traveling nut or member be slidably supported on a rod or bar 5! and movable therealong by a lead screw 52. The left-hand end of the lead screw 52, as viewed in Fig. 4, has a bevel gear 53 thereon, which bevel gear is continuously in mesh with a bevel ring gear 54 of a differential mechanism, designated generally as 55. The differential mechanism includes side gears 56, 5? connected to shafts 58, 59, respectively, opposite ends of which shafts are connected by miter gears El], 6! to the shafts 18,28.

The limit switches 43, to are connected in series circuit with the forward and reverse contacts, respectively, of the controls for the motor 25 and the limit switches M, 45 are connected in series circuit with the forward and reverse contacts, respectively, of the controller for the motor 21. The limit switches 52, 48 are forward and reverse slow-down switches and operate to reduce the speed of the motor 25 before it is stopped by the forward and reverse stop switches 40, 44, respectively. In like manner, the limit switches 43, A! are forward and reverse slow-down switches for the motor 27. The construction is such that when the motors 25, 21 are caused to operate in a forward direction, that is, clockwise a viewed in Fig. 2, the trolley iA. and the boom B are both retracted or moved toward the right at an equal rate of speed. Because of the differential mechanism C, the member 50 remains stationary and if the trolley is adjacent to the rear end of the boom B, as illustrated in the drawings, the position of the member 50 is adjacent to the limit 4 switches 42, 43. If the trolley A happens to be at the forward end of the boom B, the member 59 will be positioned adjacent to the limit switches 45, 4?.

If the direction of rotation of both motors 25, 21 is the reverse of that referred to above, the trolley and boom will be moved in the reverse direction to project the same, however, the position or positions of the member 50 will remain the same. For any intermediate position of the trolley A between the ends of the boom B, the member 5% will assume a correspondingly intermediate position between the two groups of limit switches.

With the various parts in the position shown, the motor 25 cannot be operated in a forward direction to move the trolley A further toward the rear end of the boom B without first actuating the motor 2'? to further retract the boom because substantially concurrently with the actuation of the motor controller to cause the motor 25 to operate in the direction mentioned, the member 53 will be moved toward the left as viewed in Fig. i an amount sumcient to open the limit switch 2-2, thereby reducing the speed of the motor 25 and if the operation is continued without starting the motor 27 in a direction to retract the boom, the limit switch iii will be opened and the motor stopped. In a similar manner the motor El cannot be operated in a direction to project the boom without operating the mofor '25 in a direction to move the trolley B toward the front end of the boom because operation of the motor 27 in the required manner will move the member 55 toward the left which will open the slow-down limit switch s3 and in due time the stop limit switch 4!.

With the parts still in the position shown, if either motor is operating in a direction to effect a relative movement of the trolley toward the front end of the boom B, the member so will move toward the right along the lead screw 52 until the slow-down switches it, l? are opened whereupon whichever motor happens to be operating will slow down and subsequently stop when the member 58 opens the stop limit switches 46, 45. In like manner, when the trolley A is adjacent to the front end of the boom B, the motors 25, 2'! cannot be operated so as to cause engagement between the trolley A and the front stop l5. As will be readily understood, the limit switches are so located in the control circuits for the motors that they do not interfere with the operation of the motors to effect relative movement between the trolley and boom in an opposite direction when opened incident to operation of either or both the motor in a particular direction. The differential limit switch mechanism is so adjusted that the motors slow down and stop just before the trolley A strikes the end stops 35 or the end stops strike the trolley, as the case may be.

The starting and stopping of the motor 25, 21 are preferably under the control of an operator; however, if desired,'norma1iy open limit switches may be substituted for the normally closed limit switches shown and so arranged in the motor control circuits as to start the second motor when the trolley A reaches a predetermined position with respect to the ends of the boom B.

From the foregoing it will be apparent that the objects of the invention heretofore enumerated and others have been accomplished and that there has been provided an improved automatic control mechanism for a retracting boom crane having power actuated means for both retracting the boom and moving the trolley. Alternatively either motor may be omitted and the boom or trolley reciprocated thereby moved manually. In this event the control mechanism shown will operate to prevent operation of the remaining power actuated means to cause engagement between the trolley and the end stops on the boom.

As a further alternative construction the boom motor 21 may be omitted and the boom B reciprocated by running the trolley A against one of the end stops and thereafter continuing the operation of the trolley motor 25 until the boom B has been moved the desired distance. In this event it is necessary to insert a manually controlled switch in the control circuit for the motor 25 in such a manner as to cut out the stop limit switches, otherwise the motor 25 could not be operated to engage the trolley A with the end stops and move the boom.

While the preferred embodiment of the inven-' tion has been described in considerable detail, the invention is.not limited to the particular construction shown and it is my intention to hereby cover all adaptations, modifications and uses thereof which come within the practice of those skilled in the art to which the invention relates and within the scope of the appended claim.

Having thus described my invention, I claim:

In a retracting boom crane, the combination of a, movable boom assembly, a trolley assembly supported by said boom assembly for movement ,therealong, means comprising an electric motor for receiprocating said boom, means comprising an electric motor for reciprocating said trolley, and means operatively connected to both of said assemblies and to the control means for said motors for stopping either or both of said motors immediately prior to the trolley assembly assuming a position adjacent to either end of the boom assembly.

HAROLD G. HILLS.

7 REFERENCES CITED The following references are of record in the 20 file of this patent:

UNITED STATES PATENTS Number Name Date 878,797 Harding et a1. Feb. 11, 1908 25 2,061,044 Ringe Nov. 17, 1936 1,694,084 Straight Dec. 4, 1928 

